Syntaxin is a family of membrane-anchored SNARE proteins that contributes a helix to a membrane-fusion complex. In neuronal secretion, syntaxin and SNAP-25 on the target cell membrane assemble with synaptobrevin on a synaptic vesicle. Syntaxin contributes one helix, synaptobrevin one and SNAP-25 two, producing a four-helix SNARE complex from three protein chains. Assembly across opposing lipid bilayers couples molecular binding to membrane fusion. [ref]
Molecular Biology of the Cell, 4th edition by Bruce Alberts and others. Chapter 13, Molecular Mechanisms of Vesicle Budding and Fusion
The membrane context matters. Reconstituted complementary SNARE proteins in different liposomes can promote fusion, while a complex assembled after fusion has its membrane anchors on the same lipid bilayer. Detecting a syntaxin-containing complex therefore does not by itself show that it is still bridging a vesicle to its target. [ref]
SNAREpins: minimal machinery for membrane fusion by T. Weber and others. 1998, reconstitution and membrane-bridging SNAREpins
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